This invention relates to electronic valves i.e., devices which generally convert DC power into pneumatic output signals so that fluid flow through such valves may be controlled. More particularly, the invention is concerned with a piezoelectric crystal actuated bleed valve assembly used in conjunction with such valves such that they may be operated at extremely low power output levels. Certain known crystalline materials exhibit a piezoelectric effect, that is, they expand upon energization, generally the application of electrical energy thereto. The power needed to effect such phenomena consumes extremely little electrical energy inasmuch as such piezoelectric crystals essentially operate as electrical capacitors and thus are almost totally voltage activated.
Suggested valve constructions of this general type are set forth in the following U.S. Pat. Nos. 3,029,743 issued Apr. 7, 1962; 3,524,474 issued Aug. 18, 1970; 3,981,480 issued Sept. 21, 1976; 2,651,326 issued Sept. 8, 1953 and 3,038,500 issued June 12, 1962. In U.S. Pat. No. 3,029,743 such a piezoelectric crystal is mounted in a cantilever position through an interconnected conical element to open and close a fluid orifice. In U.S. Pat. No. 3,524,474 an edge grip mounted piezoelectric crystal to which a valve member 44 is attached is utilized to directly close an orifice 18; while in U.S. Pat. No. 3,981,480 a piezoelectric element in sleeve form is utilized in direct contact with orifices 16 and 20 to restrict or permit fluid flow therebetween. The remaining cited patents are of general interest. The above citations and discussion of these patents constitutes applicant's prior art statement.
Notwithstanding the above prior art constructions, the need still exists for a reliable bleed valve assembly neccessitating low power usage and which may accordingly be operated by a self-contained power source such as a battery, solar cell or the like. It is therefore a primary object of the present invention to provide a bleed valve assembly in which a piezoelectric crystal is energized to move or bend in such a manner so as to force a separate valve element into sealing contact with a valve seat.
A further object of the invention is the provision of a valve of the aforementioned type in which various components thereof are interchangeable without affecting the operation thereof.
A still further object of the present invention is the provision of a bleed valve of the aforementioned type in which mazimum power may be achieved from the deflection of the piezoelectric crystal so as to effectively open and close a bleed orifice which in turn controls the operation of a main valve with which such bleed valve is coupled.
These and other objects of the present invention are achieved by the provision of a bleed valve having a housing, a valve seat mounted in said housing adjacent to and communicating with said bore, a fluid flow orifice terminating at said valve seat, a substantially planar piezoelectric crystal beam-mounted within said bore by contact with said bore solely at spaced peripheral edge portions thereof such that central portions thereof are free to move laterally with repect to said valve seat, a separate valve element disposed between said crystal and said valve seat, said element cooperatively supported in such position by mutual contact with said crystal and said valve seat, and means for energizing said crystal so as to laterally bend said central portions so as to move said element respectively into contact with and away from said valve seat to open and close said valve assembly.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawing.